My present invention relates to a tooth cap for construction machinery and, more particularly, to a tooth cap having a socket portion which fits onto a stub of a bucket, shovel, scoop or other excavating unit of a construction machine, a wedge-shaped portion for biting into the ground and having two surfaces or flanks which converge toward one another and adjoin in a tip forming a cutting edge.
Tooth caps for construction machinery are wear parts of buckets, scoops, shovels, scoopers and like earth-engaging units of such machinery and are known in a variety of configurations. In general, the apparatus has a frustopyrimidal holder on the bucket, scoop or shovel which receives a tooth cap which is a chisel-like member replaceable on the holder in the case of breakage or wear.
The tooth cap can have an opening or socket which form-fittingly receives the holder and can be held thereon by an appropriate fastening element such as a pin which, for replacement of the tooth cap, can be knocked out to release the tooth cap from the holder. The socket forms a one-piece body with a wedge-shaped portion which constitutes the chisel part of the cap. The chisel part can be formed by a pair of broad surfaces or flanks which converge toward the tip of the tooth cap and may form a cutting edge at that tip. The result is a wedge-shaped body in which the convergent flanks form working surfaces.
It has been found that when such a tooth cap is driven into the ground, there is a tendency for the resistance of the ground to penetration to continuously increase with such penetration so that there is significant compaction of the ground and resistance to penetration ahead of the tip or edge of the tooth cap. Not only does this increase the force necessary to operate the machine, but it also increases the wear on the tooth cap.
It is, therefore, the principal object of the present invention to provide a tooth cap which is capable of penetration into the ground with a minimum of force and which results in only limited compaction of the earth in the course of such penetration and thus has reduced wear.
Another object of this invention is to provide a tooth cap for construction equipment which has improved ground penetration and can be utilized with greater efficiency than earlier systems.
Another object of the invention is to provide a tooth cap for the purposes described which avoids drawbacks of prior art tooth cap arrangements.
These objects and others which will become apparent hereinafter are attained, in accordance with the invention by providing a tooth cap of the type described in which at least one of the working surfaces or flanks is provided with a plurality of longitudinal ribs and/or transverse ribs.
It has now been found that, when the wedge-shaped portion which extends from the socket to the tip or cutting edge has a plurality of longitudinal ribs on at least one of the flanks of the pair of mutually-converging flanks defining the wedge-shaped portion and the ribs are relatively close together, the penetration of the tooth cap into the ground or the like is greatly facilitated because the ribs induce a displacement of the earth or rock without significant compaction of the ground while the spaces between the ribs appear to remain generally free from the earth and thus provide quasi-free spaces which remain as the tooth drives into the ground. As a consequence the friction against the tooth cap is reduced, the penetration with a certain driving force is increased and the wear on the tooth is reduced.
The spaces between the ribs serve to loosen the soil or the ground and thereby contribute to a reduced compaction because the amount of force required to drive the teeth of the tool into ground is reduced and the wear on the tooth cap is likewise reduced, lighter capacity machinery may be utilized for a given job.
Transverse ribs can be used in addition or alternatively and the transverse ribs appear to operate by presenting to the ground into which the tooth is driven, a wave-like pattern which likewise serves to displace the material and leave free space, generally behind the crests of the ribs so that again compaction is reduced along with friction against the tooth cap and the force with which the latter must be driven into ground can be reduced as well. Here again the ribs contribute to a loosening of the ground.
It has been found to be advantageous to recess at least one of the working flanks of the tooth cap and preferably the working flank provided with the ribs in a direction transverse to the longitudinal dimension or extent of the wedge-shaped pattern in a domed or curved pattern. The recess or indentation can extend between the edges of the wedge-shaped portion and the longitudinal ribs can be generally parallel to these edges.
The tooth cap as a whole can be relatively flat, i.e. the wedge angle may be small and the tooth cap can progressively be thicker toward the socket end of the tooth cap in a progressive manner. This configuration has been found to be optimum in reducing the force with which the tooth cap must be driven into the ground.
It has been found, in conjunction with such a configuration, to be advantageous to set back the height of the ribs below the edges of the wedge-shaped portion. The slightly higher edges tend to provide guides for the tooth cap which function similarly to the longitudinal ribs and facilitate penetration of the tooth cap into the ground.
Advantageously, the longitudinal ribs have a mutual spacing which is greater than the rib height and smaller than eight times the rib height. Preferably, when there is an uneven number of ribs, the central rib has a greater height than the remaining ribs and, in the case of an even number of ribs, the pair of central ribs can be of greater height than the remaining ribs. The rib height can diminish toward the edge of the tooth cap.
The longitudinal ribs can merge with rounded transitions into the flank surface and the crests of the ribs likewise can be rounded.
When the tooth cap is used for a tooth of a loader bucket or the like, it may be advantageous to form one of the working flanks with the longitudinal and/or transverse ribs of the invention while the other working flank is substantially planar and may be formed with longitudinal grooves. In this case, the planar or grooved surface may be the surface which is pressed against the ground while the surface formed with the longitudinal and/or transverse ribs is the tearing surface which lifts the ground structure. This has been found to maximize the direction-reducing effect and minimize the force required for penetration of the teeth. The longitudinal grooves in the working surface which is pressed against the ground has been found to be effective in reducing the force for displacement of the teeth by reducing the friction effect even when no loosening of the ground is effected.
When such longitudinal grooves are provided, they can be spaced apart across the width of the tooth cap and preferably these grooves can in cross section have a wavy pattern. The grooves can be provided in a number and in spacing to correspond to those of the longitudinal ribs and can have the same orientations as the ribs.
According to another feature of the invention, the edges of the tooth cap are outwardly bulged. The bulging appears to provide a form of undercut behind the advancing surfaces of the wedge-shaped portions that contributes to a reduction of friction during the penetration. The bulge can run from the tip of the wedge-shaped portion substantially the full length of the ribs and to the socket.
Especially for tooth caps which are used for excavators or where chisel-shaped teeth are required, it has been found to be advantageous to provide centrally of one or both of the working blanks a wedge-shaped longitudinal rib which can be defined by a pair of converging longitudinal ribs which meed substantially at the leading edge or tip of the tooth cap. Between these converging ribs, a flat or shallow valley may be formed and flanking these longitudinal ribs, there may be a pair of deeper valleys. The wedge-shaped longitudinal rib structure provides additional stiffening of the tooth cap and has also been found to be highly effective in a ripping and slight loosening action. The converging longitudinal ribs, moreover, have the effect of a fork in their loosening action.
It has been found to be advantageous, moreover, to provide the surfaces alongside the ribs with indentations or outwardly convex curved contours. Especially advantageous is an embodiment in which a central rib structure is provided, according to the invention, and transverse ribs are formed in the working flanks outwardly thereof. These transverse ribs can have a sawtooth configuration and can be provided with flanks turned toward the cutting edge or tip of the cap which are shallower or less steeply inclined than the flanks turned toward the socket portion.
The chisel action of the resulting cap has shown that it is effective in all kinds of excavators, grabs, back-hoes, front-loaders and the like. The transverse ribs also form undercuts or spaces behind the rib crests which reduce friction and hence the force required for operating with the respective teeth. The transverse ribs can be uniformly spaced from one another and as has been noted, one or both of the working flanks may be provided with the longitudinal and/or transverse ribs.
The tip of the tooth cap can be linear or arcuate transverse to the longitudinal dimension and centrally of the tip, a linear chisel edge can be formed which can be connected to arcuate or stepped edge regions connected to the lateral flanks of the tooth cap. The transverse ribs can be somewhat arcuate and can have centers of curvature located toward the end of the tooth cap which is remote from the tip and close to the axis of the pin holding the tooth cap onto the frustopyrimidal stump.
The transverse ribs also may be inclined outwardly away from the central rib. These configurations of the transverse ribs help the tooth cap in shedding loosened material and thereby contribute to a reduction in the compaction.
The spaces between the transverse ribs may also be grooved to form a channel structure which assists in the passage of the crushed or ground center and loosened soil away from the tooth cap when the latter is utilized in a chisel action.